It seems from answers to certain questions (such as Should a mid-career faculty application include a letter from the former PhD advisor?) that the role of an advisor may continue after a student has graduated.
In general, what is the professional role of a PhD advisor after a student has graduated? Are they simply possible collaborators and sources of recommendation letters, or is there more?
I've seen this question: What is exactly the role of a phd advisor? which is related, but focuses on the role of an advisor during graduate school.
When should you stop asking your PhD advisor to do advisor like things? is related, but my question is what are the advisor-like things a PhD advisor might/should do after a student has graduated.
Here are some other related (but not duplicates as far as I can tell) questions: